Freezing high liquid content fruits and vegetables



Nov. 9, *1948. A. F. HQ'FEMAN 2,453,130

FREEZING HIGH LIQUID CONTENT FRUITS AND VEGETABJES mvg/mak .2 ALBERT F.' HQFFMAH /llb ATFORNE Y Nov. 9, 1948. A. F.HOFFMAN 2,453,130

FREE-ZING HIGH LIQUID CONTENT FRUITS AND VEGETABLES Filed April 28, 1945 2 sheets-sheet 2 INVENTOR ALfRr f HOFFMAN y @ATTORNEYS Patented Nov. 9, 1948 I D VEGETABLES FREEZING HIAgH LIQUID CONTENT FRUITS Albert F. Hoffman, East Orange, N. J.

l Application April 28, 1945, Serial N0. 590,936 9 claims. (ci. 99-193) This invention relates to methods and apparatus for freezing food products, and has particular reference to methods and apparatus for quick-freezing tomatoes and -other vegetables and fruits of similar bulk and liquid content.

The art of quick-freezing food products has been highly developed, particularly in the treatment of vegetables, meats, and the like. Each of these food products has presented certain problems that had to be solved in order to obtain a product of satisfactory appearance and flavor. A good many of these food products can be and have been frozen by direct contact with a refrigerant liquid for the reason that they have skins or surfaces that repel or prevent absorption where the slices are spread apart and subjectof the liquid into the product. ed to a low temperature, for example 10 to 50 Other food products which are more permeable below zero Ii.,v so that the surfaces of the slices have been frozen by placing them in a blast of are frozen .before any substantial amount of cold air refrigerated to a sub-zero temperature. moisture can evaporate or drain from the surthus obtaining a quick-freezing of the product faces. without the formation of ice crystals of such More particularly, the tomato preferably is size as to damage or to Cause detellOratiOn 0f the partially sliced into a plurality oi' connected cell structure. Still other products. Such 8S 35h, slices by very keen, thin knives so that the shape have been frozen by Passing blocks 0f the nSh of the tomato and its cell structure are not subbetween metallic plates 0r belts and aDDlYmZ a' 25 stantially altered. The slices are then spread refrigerant solution to the plates in order to obapart and immediate@ subjected to the Amuon tainahigh rate of heat exchange. of a freezing medium, preferably very cold air, Attempts have been made in the PHSt t0 freeze which immediately hardens the surfaces of the tomatoes and similar fruits and Vegetables by slices and causes a quick-freezing of the slices.A these processes, but Such attempts have not been s very important the cut surfaces of the successful. Toma/GOES Contain about 93% Water slices be frozen almost immediately upon their by Weight. This Water 1S not tightly bound into separation so that oxidation and loss of moisi the Cells 0r pulp 0f the tomato and as 9' conse', ture are avoided. Some advantage is gained by quencc, the tornato is easily dehydrated and oxiusing com knives inasmuch as they cause the dized when it is cut or sliced and exposed to airmoisture to congeal and thereby set the sur- Moreover, the moisture tends to drainfrom` the tomato with the result that it acquires a peculiar and unappetizing appearance, even after standing for a short period of time in the air.

It has not been practicable to freeze whole tomatoes for the reason that the ice formed on the surface portions of the tomato as the freezing progresses, acts as insulation and thus slows downl the rate of heat transfer. This slowing of the heat transfer results in a relatively slow freezing of the center of the tomato with the result that large ice crystals are formed that destroy the cellular structure of the tomato or damage it so badly that when the tomatol is thawed and sliced, it has a very unappetizing mushy appearance.

An object of the present invention is to provide a method of quick-freezing tomatoes and the like, whereby the moisture content of the tomato is not substantially changed and the appearance 2 and flavor are not impaired by the quick-freezing operation.

Another object of the invention is to provide apparatusfor processing and quick-freezing tomatoes in such a manner as to preserve the appearance and flavor of the tomato.

Other objects of the invention will become apparent from the following description of typical methods and apparatus i'ox` quick-freezing tomatoes.

In accordance with the present invention in which the treatment of tomatoes will be described by way of example, the tomatoes are first sliced and then transferred to a quick-freezing zone faces of the slices. Following quick-freezing, the slices may be pressed together again and the tomato wrapped and packaged and stored at low temperature in order to dition.

Tomatoes frozen in the manner generally described above, maintain their color, flavor and preserve its frozen concellular structure for long periods of time and may be thawed and used exactly in the same manner as fresh tomatoes. If desired, tomatoes may be used in their frozen state, and in this holder for receiving and conveying a tomato through a slicing and freezing device;

Figure 5 isa view in side elevation of a portion of the conveyor illustrating the tomato holder and defrosting scrapers; and y Figure 6 is a view in end elevation of a modifled form of a freezing device showing the scrapers passing through the device.

The form of freezing apparatus chosen for purposes of illustration may consist of a tunnel or chamber lo formed of metal, wood, or other material which is suitably insulated to avoid heat losses. Passing through this elongated tunnel is a conveyor- II which is supported at opposite ends by means of sprockets I2 and I3, which are rotatably mounted on the shafts I4 andy I5, respectively. The shafts may be supported in suitable Journals IB and I1 extending outwardly from opposite ends of the tunnel I0. One or both of the shafts I4 and I5 may be driven in any suitable way, such as for example, by means of the motor Iii through a reduction gearing I 9 and chain and sprocket drive 20.

The conveyor II may be made up of a plurality of links 2 I, 22, 23, etc. As shown in Figure 5. the links 2| of the conveyor I I may be provided with a chuck or holder 24 formed of a. rubbery material, which is provided with a concavity 25 for receiving a whole tomato. 'I'he holder 24 preferably is made up of a plurality of resilient fins 26 extending longitudinally of the holder in order to permit the passage of slicing knives therebetween.

As illustrated in Figure 1. a plurality of links 2I having the holders 24 thereon may be arranged in sequence on the chain, for example. two or more of these holders may be connected end to end.

The links 22 may be of generally H-shaped construction and act as separators between the links 2l and the links 23, which are provided with scrapers, the purpose of which will be de scribed hereinafter. The Scrapers preferably are formed of rigid material and may consist of elongat d iin-shaped elements 21 which are substantia ly the same thickness as the slices of the tomato which are formed as described hereinafter. The elements 21 are connected at their lower edges to the link 23 by means of hinges 28 to permit them to be spread fanwise (Figure 6).

Referring against to Figure l, the ripe, but firm tomatoes T after being washed and chilled to slightly above freezing temperature, that is, 32 F.. are passed into the tunnel through a flap-like door 29 and thence into an inner chamber 3c where the tomatoes are sliced and frozen. The inner tunnel or chamber 30 extends substantially the length of the tunnel It and ,is provided with a hinged flap-like inlet door 3i through which the tomatoes and the conveyor II pass. Within the chamber 30 are a plurality `of parallel slicing knives 32 which are formed of thin steel and are supported under tension by means of a U-shaped bracket 33 connected to the top 30a of the tunnel 30. The edges of the knives 32 may be provided with fine teeth 32a which aid in cutting through the skin of the tomatoes as well as the pulp without damaging its cell structure appreciably. If desired, thin razor-like knives may be used, or

nature of the fruit or vegetable.

even thin rotary knives. The knives should be.

of such thickness and sharpness that the slices may not be immediately separated or compressed sufficiently to squeeze the juice from the slices. The optimum number of slices and consequent spacing of the knives depends upon the size and For example, one-fourth inch slices have been found desirable for tomatoes. making nine slices for a good-sized tomato.

A thin metal tape 34 is connected to the rear end of each of the knives or the leg of the bracket lsupporting a knife so that it will engage in the slot cut by the knife.

through to form separate slices that are ,held

together by the resiliency of the holder 24.-I

The tapes 34 diverge suiliciently to, spread the f slices apart and then extend in parallel relation-v ship lengthwise through the quick-freezing section 3B. which forms a part of the tunnel I0. The tapes 34 may extend a greater portion of the length of the freezing section 35, and are. supported in parallel relationship by projecting rods 86 and 31.

The tapes 34 are of suiilcient width, for example, between about one-quarter and one-half inch each, so that they not only spread the slices apart, but maintain the slices in spaced apart relationship by engagement of their upper and lower edges with the adjacent-slices as shown in Fig, 3.' The outermost tapes 34 are sufficiently wide to prevent the outermost slices of the tomatoes from falling to horizontal position or be-k l low horizontal.

The freezing chamber or tunnel 35 may be provided with any desired type of quick-freezing or refrigeratingequipment. For example, as shown in Fig. 1, the chamber 3B may be refrigerated by means of circulated cold air refrigerated to a quick-freezing temperature. The circulating sys. tem may include a blower 38 having its intake connected by means of suitable conduits 39 and 40 to the discharge end of the chamber 3l, and its pressure side connected by means of suitable conduits 4I and 42 to the inlet end of the charnber 35. The pressure side of the blower I8 may be connected to a chamber 43 which is provided with a cooling coil 44, supplied with refrigerant by means of a conventional motor-compressor system 4B. Thus. with the compressor system 45 and the blower 38 in operation, a strong blast of cold air is passed over and between the tomato slices to quick-freeze them.

Some of the refrigerated air will be lost. of course, from the refrigerating section 35 of the tunnel. This chilled air will pass through the tunnel 80 and into the main chamber or tunnel I0 so that these chambers are maintained at low temperatures thus aiding in the conditioning of the tomatoes for the quick-freezing operation and ends of the freezing chamber 3B and the tunnel i0, respectively. reduces the amount of the reslices together by means of converging plates Il adJacent the discharge end of the tunnel i0. The

lpartially thawed web T will quickly refreeze because of absorption oi' the heat therein by the remainder of the tomato. If the tomatoes are cut into separate slices, the thawing bath can be omitted. The now hardened, frozen and reshaped tomatoes may be passed through suitable wrapping and packaging devices and transferred in the usual way to a cold room where they are maintained at about zero temperature until ready for distribution.

The apparatus described above is susceptible to considerable modification without altering the resuits obtained therewith.- For example. it maybe desirable to provide resilient retaining plates l on opposite sides of the slicing knives 32 in order to rna'ite4 certain that the slices will not fall apart before they are separated by the tapes Il. The retaining plates 50 are bestv shown in Figures 1 and 4.

Also, if desired, the slices may be frozen by direct contact with chilled fins which are introducedfb'etween the slices after they have been separated by the tapes Il. In' this form of the device, the tapes 34 are shorter than illustrated in Figure 1 and the freezing section 351s replaced by an elongated Jacket of the kind illustrated in Figure 6 of the drawings. This Jacket 5i may be semi-cylindrical in shape and is provided with substantially radially extending openings l2 bef cut surface of the tomato-may become frosted due to moisture from the slices. The scrapers 21 are lprovided to remove the frost not only from the cutting knives, but from the surfaces of the tapes 34 and the fins 53 of the refrigerating chamber, if used. These hinged scraper elements 21 follow substantially the same paths as the corresponding tomato slices and thus engage the same surfaces that the tomato slices engage. 'I'he frost removed from the blades and other elements drops through the open links 22 and can be removed from time to time from the' bottom of the tunnel 30.

It is, of course, possible to use direct brine freezing for refrigerating the slices by providing the chamber 36 with suitable brine sprays. However,

lthis practice is not as satisfactory as those deticing. the invention, it will be understood that the method and apparatus are susceptible to consi-derable modification without departing from the invention. For example, although the invention has been described in connection with tomatoes, it is equally applicable to other fruits yand vegetables of similar bulk and liquid content, which may not be supplied tc remote markets by reason of spoilage or which must be picked or harvested before ripening, with consequent 'loss of or decrease of valuable vitamin, mineral or fiavor'content. and the like. Other examples are mangoes. oranges. lemons, onions, cucumbers, potatoes, and the like, and in the case of vegetables, they may be parboiled, blanched, or otherwise partially cooked before slicing and freezing. Hence,- the term tomato when used herein an-d in the appended claims is understood to comprehend such equivalent fruits and vegetables. The forms of the apparatus and the methods described herein should be considered as illustrative and not as limiting the scope of the following claims.

I claim:

1. A method of quick-freezing an edible article of the class of vegetables and fruits, which comprises cutting the article into a plurality of slices connected at one edge, spreading said slices apart to expose their cut surfaces, and subjecting the cut surfaces of said slices lto a refrlgerating means maintained at quick-freezing temperature.,

2. A method of quick-freezing an edible article of the class of vegetables and fruits, which comprises slicing the article into a plurality of slices connected at one edge to the other slices by an unsliced portion of the article, spreading .the slices apart, immediately bringing the surfaces of said slices into contact with refrigerating means maintained at quick-freezing temperature, until said article is quick-frozen, and pressing said slices together.

3. A method of quick-freezing edible articles of the class of fruits and vegetables, which comprises the steps of chilling an article to slightly above 32 F., cutting the article into a plurality of slices Without substantially separating the slices, separating the slices .to expose the cut surfaces of said slices, subjecting the slices to a'refrlgerant maintained at quick-freezing temperature, and thereafter pressing said slices together to restore said article substantially toits original shape.

4. An apparatus for quick-freezing an edible article of Ithe class oi' vegetables and fruits comprising a refrigera-ting tunnel, a conveyor extending through said tunnel, a plurality of means on said conveyor each adapted to receive an article,

f a plurality of cutting elements spaced apart transversely, and extending lengthwise of said tunnel adapted lto engage each article and cut it into a plurality of slices, means in said tunnel for spreading said slices apart fanwise to expose their cut faces, refrigerating means for chilling a portion of said tunnel to quick-freezing temperature to quick-freeze said slices, and means for pressing said frozen slices together to restore said article substantially to its original shape.

5. An apparatus for quick-freezing an edible article of the class of vegetables and fruits, cornprising an elongated chamber, a conveyor extending through said chamber, a. plurality of holders on said conveyor, each adapted to receive an article to 4be frozen, each holder including a plurality of resilient spaced apart segments extending lengthwise of said conveyor, a plurality of cutting elements in said chamber adapted to 'pass between said segments and partially out said article into a plurality of slices connected at one anarco edge. ineens in said chamber for separating said slices to 'expose their cut surfaces, and means for chilling al portion i' said chamber to quick-freezing temperature .to quick-freeze said slices.

. 6. An apparatus Sor quick-freezing an edible article of the class ot vegetables and fruits, comprising a' refrigerating tunnel, a conveyor extending through said tunnel, a plurality oi' means op chilling e. portion of said tunnel to quick-freezing temperature to quick-freeze said slices. v

7. An apparatus for quick-freezing an edible article o1' the class of vegetables and fruits cornprlsing a refrigerating tunnel, a conveyor extending through said tunnel, a plurality of means on said conveyor each adapted to receive an article, a plurality of cutting elements spaced apart transversely of said tunnel adapted to engage each article and cut it into a plurality of slices, means in said tunnel for spreading said slices apart to expose their cut faces, heat exchanging mean-s in said .tunnel having hollow fins engageable with the cut surfaces of said slices, and means for circulating a refrigerant lthrough said hollow fins.

8. An apparatus for quick-'freezing an edible article of the class of vegetables and fruit comprising a reirigerating tunnel, a conveyor extending through said tunnel, a plurality o'f means on said conveyor each adapted to receive an article, a plurality oi' cutting elements spaced apart transversely o! said tunnel adapted to engage each article and cut partially through it to divide it into a `plurality of connected slices, means in said tunnel for spreading said slices apart to expose theircut faces, refrigerating means for chilling a portion oi' said tunnel to quick-freezing temperature to quick-freeze said slices, and means on said conveyor for engaging, scraping and d airosting said cutting elements.

9. An apparatus for quick-freezing an edible article ofthe class of vegetables and fruits, comprising a refrigerating chamber, a conveyor extending through said chamber, a plurality o1' l means on said conveyor each adapted to receive an article. a plurality oi' spaced apart cutting elements in said chamber adapted to engage eacharticle and cut it partially through .to divide the article into a plurality of connected slices, means in said chamber for spreading said slices apartA to expose their out laces. refrigerating means for chilling a portion of said chamber to quick-freezing temperature to quick-freeze said slices, means adjacent to said conveyor for pressing said frozen slices together, and a plurality of resilient tin-like Scrapers carried by said conveyor adapted to pass between and scrape the surfaces of said cutting elements.

ALBERT F. HOFFMAN.

REFERENCES CITED The following references are oi' record in the le of this patent:

UNITED STATES PATENTS OTHER REFERENCES.

8vgod Industries, August 1944 (vol. page 632) Bulletin 201. Geo. Exp. St., Microscopic Studies of Frozen Fruits and Vegetables, page 27. v 

